Competitive C-H Activation and C=C Coordination in the Reactions of Acetylenes with a Binuclear Rhodium Complex.
Abstract
The reaction between phenylacetylene and the binuclear complex Rh2(CO)3(dppm)2, 1, has been studied in detail. At 28.5 C in benzene, the reaction leads to formation of a phenylvinylidene bridged A-frame complex Rh2(CO)2(dppm)2(C double bond C(H)Ph), 2a, while in refluxing acetone it yields the alkyne bridged complex Rh2(mu2-Eta2-PhCCH)(CO)2(dppm)2, 3. The kinetics of the reaction show that vinylidene formation is cleanly first order in PhCCH and in 1 with k sub H/K sub D of 2.7, while formation of 3 proceeds with no significant isotope effect and a kinetic dependence on PhCCH suggestive of a preequilibrium involving 1 only. The effect of CO on the reaction leading to 2a and 3 supports the notion that this preequilibrium involves CO dissociation from 1. The results clearly establish that the mu2-Eta2-alkyne bridged complex does not lie on the reaction path of the metal-promoted acetylene-to-vinylidene transformation, and suggests that vinylidene formation proceeds with initial C-H activation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 20, 1986
- Accession Number
- ADA164086
Entities
People
- Donald H. Berry
- Richard Eisenberg
Organizations
- University of Rochester